CANDIDATE/TRAINING: My goal for this career award is to obtain the necessary training to become an independent investigator in the molecular pathogenesis of Leishmania infection. I am a pediatric infectious diseases fellow who earned a Ph.D. in microbiology studying the parasite Toxoplasma gondii. During my fellowship, I began to study the mechanisms that regulate the uptake of Leishmania by macrophages. My Ph.D. provided me with experience in microbiology and cell biology, and I developed experience with mouse models of pathogenesis during my fellowship training. I now plan to develop additional expertise and mentored research experience in biochemistry and pharmacology, and relate it to the pathogenesis and treatment of leishmaniasis. My mentor is a biochemist who studies the mechanisms that regulate actin polymerization. I will also be mentored by a parasitologist with extensive experience in Leishmania infection and its regulation by the mouse immune system, a cell biologist who works on the mechanisms of integrin activation, and a pharmacologist. The combination of my previous research background, my clinical training, my research during my fellowship, and my mentored research and coursework during the K08 award period will enhance my scientific breadth of knowledge, and uniquely enable me to contribute to the field of molecular parasitology. PROJECT: Leishmania is a parasite that causes cutaneous or visceral disease. Current therapies have significant side effects, and parasites are developing resistance to them, so new therapies are needed. Leishmania must live inside phagocytes to survive. Both life cycle stages, promastigotes and amastigotes, infect macrophages. Studying how Leishmania is engulfed by macrophages will help us understand its pathogenesis and could define new antiparasitic targets. My work shows that Abl family kinases permit uptake of Leishmania by macrophages, and that inhibiting these kinases ameliorates leishmaniasis in mice. This project further defines the mechanism by which Leishmania is engulfed by macrophages and causes disease, with the eventual goal that drugs that inhibit uptake will provide novel therapeutic strategies. I hypothesize 1) interactions between ?2 integrin and Abl allow promastigote uptake by macrophages, 2) interactions among FcR, Src family kinases, and Arg allow amastigote uptake by macrophages, and 3) drugs that can inhibit these signaling proteins will decrease the manifestations of cutaneous leishmaniasis in mice. In Specific Aim 1, I will characterize the ?2 integrin:Abl interaction and its role during promastigote uptake by macrophages. In Specific Aim 2, I will determine how Src family kinases affect amastigote uptake by macrophages and the severity of cutaneous leishmaniasis in mice. In Specific Aim 3, I will assess whether inhibitors of parasite uptake by macrophages, alone or in combination with miltefosine, decrease the severity of cutaneous leishmaniasis in mice. My studies will elucidate the initial steps of parasit uptake, improve our understanding of the pathogenesis of leishmaniasis, and provide novel approaches to treat this devastating infection.